Our eco-experts help two Colorado homeowners make an old mining cabin sustainable.
There’s rich history in the mountains west of Boulder, Colorado, where gold was discovered in the 1800s and is still mined in towns such as Gold Hill today. Along with rags-to-riches and hard-luck tales, the boom era has left a legacy of abandoned mines and old mining shacks that are now being reclaimed and renovated.
Tracy Ferrell and her husband, Tim Zych, are two of the new pioneers who have a passion for sustainability—ironic given that their home comes from an era that was anything but green. The couple bought a 150-year-old mining cabin in Gold Hill and are now remodeling it to accommodate their family. Tracy’s question is: Can an old structure once associated with extractive mining practices now attain the energy-efficient, resource-conserving, healthful standards of green building?
Tracy and Tim want to make their cabin, which is a historical landmark, as green as possible, but they’ve found it difficult given local historical society constraints. Space is an issue, and they aren’t allowed to alter the outside of the building significantly (including adding rooms) because of historical renovation laws. Working within these constraints, the pair has chosen to remodel their home using healthy materials that don’t outgas or release toxins.
Up on the housetop
The first major challenge is to make a virtually uninsulated cabin energy efficient. Living in the Colorado mountains is pretty challenging in winter when temperatures can dip well below zero and winds can reach 100 miles per hour. Finding the right combination of air sealing and insulation to protect the building’s historical façade is crucial.
We started with the roof, which had recently been covered with the cheapest shingles possible. Because the attic space is now the bedroom, headroom is limited. My suggestion was to cover the existing two-by-four rafter roofing with a product that incorporates two or three inches of polyisocyanurate rigid foam with a nailing surface laminated to the top. The new polyiso foam product from Atlas Roofing doesn’t contribute to ozone depletion or global climate change like conventional polyiso insulation. Polyiso also has an R-value of 7.5 per inch, which gives the home a net roof insulation of R-35, including the four inches of insulation in the rafters. Colorado code for roof insulation is typically R-30, so this additional R-5 will make the home markedly more comfortable while lowering Tracy and Tim’s energy bills. Installing fifty-year shingles will give them long-term protection from the hearty Colorado winds and eliminate waste from more frequently replaced roofing materials.
Warming up with insulation
The next step is getting insulation under the floor. The house is built on a stone rubble foundation with a shallow crawl space underneath. Water currently flows under the cabin from the hillside above. I suggested that Tracy and Tim use water-resistant blue board (also known as closed-cell extruded polystyrene or Styrofoam) between the floor joists. The edges can then be caulked to reduce air infiltration. A laminated product made of recycled aluminum and wood fiber, called Thermo Ply, can then be installed across the joists to protect the foam from rodents and to further reduce air infiltration. The potential R-value is 24, which is significantly higher than the Colorado code standard of R-15 and will drastically improve the home’s energy efficiency. A 6-mil polyethylene vapor barrier should then be installed on top of the dirt to keep moisture away from the wood-framing members.
The walls offer the biggest challenge. The existing wood siding has to stay intact given historical code restraints, and the interior surface of the studs (vertical structural columns) is irregular. Additionally, there is no triangular bracing on the walls to provide structural support. Instead, the sheathing is made of horizontal boards that provide no “rack resistance,” or support against wind loads deforming the building.
I recommended that Tracy and Tim identify several stud cavities in which to place oriented strand board (OSB), a type of engineered wood made from smaller pieces of wood that eliminates the need for plywood made from old-growth trees. Next, it’s important that they create a structurally strong triangulation formation with the OSB and existing studs. This structure should be reinforced by gluing and nailing the OSB to the exterior sheathing in the stud cavities, and they should use a low-VOC construction adhesive such as PL Premium to avoid toxins common in conventional adhesives while mitigating wind resistance and air infiltration.
I also recommended that the couple caulk around all edges of the OSB to tighten up the envelope and make the cabin more energy efficient. In addition, I suggested they spray other penetrations through the envelope with a polyurethane expansive foam for further air sealing and then install conventional formaldehyde-free, recycled-content fiberglass from Johns Manville in the stud cavities. Finally, they need to “fur out” the insides of the studs using one-by-twos and shims to provide a flat surface to hang the drywall on.
At the time of my visit, the historical society was insisting that Tracy and Tim leave the cabin’s existing windows in place. These are old, single-glazed, double-hung windows that are rotting away and should be replaced with new low-E windows that match the old window design but reflect heat back into the house during winter. Hopefully the old windows will rot entirely so that the historical society can’t argue about replacing them.
Historic home, modern kitchen
Next, we took a look at the cabin’s interior. To start, reclaimed cabinets from the local used building material yard are a great option, and Tracy and Tim’s kitchen space is flexible enough to incorporate almost any recycled cabinets they choose. People often discard beautiful, functional cabinets during a kitchen remodel, and these are available for a fraction of the cost of new ones. As an added benefit, used cabinets have already outgased most of the formaldehyde typically found in particleboard cabinetry, whereas new cabinets can outgas the toxin for years.
While Tracy and Tim have yet to decide on countertops, a wide range of options is available depending on their budget. The couple would like to use ceramic tile, but it’s more expensive than other options, and tile grout needs to be sealed every year to prevent mold and bacterial growth on its porous surface. A less expensive option is Formica, which—if installed with a low-toxic adhesive—is an acceptable green choice. It lasts almost indefinitely and resists microbial growth.
And finally, the particleboard substrates for countertops should be sealed on the underside because like cabinets, they can outgas formaldehyde.
Tracy and Tim intend to paint the entire cabin with low- or no-VOC paints. Because walls have the most surface area, outgasing paint is a major contributor to short-term air quality problems. When painting, it’s best to ventilate the house for fifteen to thirty days before occupancy if possible so the paint has time to dry and outgas.
Because carpet outgases toxins, Tracy and Tim plan to keep the cabin’s existing wood floors and renovate the kitchen and bathroom floors with tile. I suggested they sand and finish the wood floors with BonaKemi’s Traffic, a low-VOC and relatively nontoxic water-based wood finish that has held up well in tests on gymnasium floors.
Tracy and Tim also have structural and waterproofing issues because of the age of their cabin and the haphazard nature of additions that were built into the slope above the house. They have been in ongoing negotiations with the historical society as to what can be deconstructed and what has to stay. Though there are some challenges, Tracy and Tim are making progress toward an energy-efficient, comfortable, and healthful house they can be proud of for years to come. And hopefully this mining cabin, left over from an era in which the environment was degraded to extract non-renewable resources, may soon reflect the green aspirations of today’s environmentally conscious home owners.
David Johnston is president of Boulder, Colorado-based What’s Working, a sustainable building consulting firm.